If you have a big Database and you don't want to bring much workload on the DB Server, we chose the FSC Produkt, because you could backup the BCV on another storage host and the Archive files would be backed up online, without interrupting the produktion.
If you are using RMAN its online backup and snaps are also not such a good decision for backup solutions because they are also affecting the production.
In cause of a restore its very easy with the FSC tool. With RMAN and snaps, i think there is no tool who combines these 2 functions to 1.
Why would you snaps (VDEV)? Use BCVs. I believe some symmetrix freaks would argue clones would be even better, but to make it independent of production you would need to have -precopy option enabled which I believe is going to be supported in 2.4SP1 (should be out next week). With BCVs you will not impact production.